This invention relates to a longitudinal sealer of a form-fill-seal combined bag maker and packaging machine (hereinafter simply referred to as a packaging machine), and more particularly to a device for adjusting the position of a heater in such a sealer. The invention further relates to a packaging machine incorporating such an improved sealer.
Consider, for example, a so-called vertical pillow type packaging machine which uses a former to bend an elongated web of thermoplastic sheet into a tubular form, while pulling it down over the peripheral surface of a loading cylinder through which articles to be packaged are dropped. The mutually overlapping side edges of the tubularly formed sheet are sealed together by a heater in a vertical (or longitudinal) sealer, and a horizontal (or transverse) sealer disposed below the loading cylinder seals the top edge of a bag and the bottom edge of the next bag at the same time. The vertical sealer is usually provided with a vertically extended endless belt such that the filling and sealing of the bags can be carried out continuously.
Packaging machines of this type are required to be able to produce bags of different shapes and sizes, depending upon both the nature and the amount of the articles to be packaged. For this reason, many kinds of formers with different shapes and sizes are customarily provided and they are selectively used with a packaging machine. Japanese Patent Publication Tokkai 5-124606 discloses a packaging machine, of which the position of its sealing heater can be changed, depending on which of many available formers is installed. Since there are fluctuations in the shape and size of the formers due to production errors, the position of the sealer may require additional adjustments both in the radial and tangential directions. Moreover, the sealer may have to be tilted, even after it is correctly positioned, such that its tip will be accurately opposite to the surface of the former.
Thus, whenever a different former is installed for producing bags of a different kind, it becomes necessary not only to remove the endless belt and to adjust its position but also to carry out adjustments of the position of the sealing heater. In particular, since a prior art vertical sealer is usually so structured that its heater is axially supported by a shaft in its exterior, the tangential position of the tip of the heater with respect to the former is affected as the heater is rotated against this support shaft. The position adjustment of the heater is therefore made even more difficult to perform.